There are some link masking programs that use javascript and ActiveX
to automatically create a Clickbank cookie on the visitors computer
without the visitor even having to go to the vendors site. I asked
Clickbank about this, and they said this is definitely against their
guidelines, and they would be investigating this. All hoplinks are to be
targetted to a top window, which means when you use a hoplink the
vendors site must be visible to the visitor. You cannot target hoplinks
to an invisible image. If your visitor is taken to the vendors website
with the cloaking program you are using, then you should be fine.
However, if you send the visitor to a page on your site and set the cookie
from your site before the visitor even sees the vendor site, then this is
not allowed with Clickbank. I don't know if Clickbank has taken any
action on this yet.
I don't know about the two specific programs you asked about, I haven't
checked them out to see how they work.

I could be wrong, but I believe Affiliate Defender and Affiliate Masker
open the link in frames, and do not use the method I described above.
This will still work, however Clickbank will break the site out of the
frames and so your affiliate id would still show in the address bar once
the visitor reaches the vendors site. However, I don't really see a problem
with your id showing in the address bar if you cloak your hoplink, once
the visitor reaches the vendors site, your cookie will already be created.
And if someone is familiar with Clickbank and are determined to get
the credit themselves, once they see the sales link or the order form
they will know it is a Clickbank product and will find a way to get the
credit if they really want it. All they need is the merchant's id, they do
not need your id. If Clickbank didn't break the site out of frames, there
is a good chance your cookie wouldn't be created and you wouldn't
get credit for the sale.

OK, so you want to know how to cloak your links. This seems to be the
popular thing nowadays. You can use the embed command to embed
another webpage within your webpage, and guess what, you can set
the width and height to 1 so your visitor won't even see this extra page. You
can open a hoplink within your own page completely visible to the
visitor, thereby setting the cookie without the visitor even going to the
vendors site, and then you can link to whatever page you wish. But keep
in mind, this is against Clickbank's terms. All hoplinks are to be
targetted to a top window.